1. Field of the Invention
The present invention generally relates to nonvolatile magnetic memories and, more particularly, to high-output nonvolatile magnetic memories having switching and spin torque magnetization reversal capabilities.
2. Discussion of Background
As shown in FIG. 14, conventional nonvolatile magnetic memory comprises a cell by forming a tunnel magnetoresistive (TMR) device on a complimentary metal-oxide semiconductor field-effect transistor (CMOSFET). The complimentary metal-oxide semiconductor (CMOS) is used for switching. A TMR device (e.g., see non-patent document 1) is used for recording and reading information. For additional detail on CMOS technology, see the following references.
[Non-patent document 1]
T. Miyazaki and N. Tezuka, J. Magn. Magn. Mater. 139, L231 (1995)
[Non-patent document 2]
F. J. Albert et al., Appl. Phys. Lett., 77 (2000) 3809
[Non-patent document 3]
Y. Ohno et al., Nature 402 790 (1999)
Conventional magnetic memory requires gate, source, and drain electrode wires for operating the CMOS that is used to switch TMR cells (information recording cells). Unfortunately, the conventional CMOS has a multitude of electrode wires.
A conventional magnetic memory reverses magnetization of the free layer in the TMR device to write information by using an in-plane static magnetic field generated by a current supplied to a bit line and a word line. Unfortunately, a very large amount of power is needed to induce a magnetic field enough to cause the magnetization reversal.
The conventional magnetic memory uses a TMR device whose resistance change in the TMR device is 40%, measured by an output signal of the TMR device. Unfortunately, such an output is relatively low.
The present invention provides a highly integrated, low-power-consumption, and high-output nonvolatile magnetic memory using a two-terminal-type memory cell comprising a semiconductor, a spin transfer torque magnetization reversal layer, and a TMR device. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a device or a method. Several inventive embodiments of the present invention are described below. The present invention has the following objectives.
A first objective is to decrease the number of electrode wires.
A second objective is to reduce the power required to reverse magnetization of a free layer in the TMR device independent of a current induced magnetic field.
A third objective is to increase output of the TMR device.
It is possible to provide magnetization reversal independent of switching and a current induced magnetic field by installing the above-mentioned two-terminal nonvolatile magnetic memory cell in the magnetic memory. Thus, it is possible to decrease a memory cell area and provide a large-scale integration.
In order to achieve the aforementioned objects, the present invention provides a nonvolatile magnetic memory having a bit line, a word line, and a layered element formed by being electrically connected to the bit line and the word line, wherein the layered element has a structure comprising a pn diode, a first ferromagnetic layer, a nonmagnetic layer, a second ferromagnetic layer, a tunnel barrier between ferromagnetic layers, and a third ferromagnetic layer all of which are layered in this order; the word line is electrically connected to the diode; and the bit line is electrically connected to the third ferromagnetic layer.
In such multilayer structure, the first ferromagnetic layer, the non magnetic layer, and the second ferromagnetic layer form a giant magnetoresistive (GMR) film. The second magnetic layer, the second tunnel barrier, and the third ferromagnetic layer form a TMR film. Of the GMR film, the first ferromagnetic layer, and the non magnetic layer function as spin transfer torque magnetization reversal layers. The second ferromagnetic layer functions as a ferromagnetic free layer for the GMR/TMR film. The first ferromagnetic layer functions as a static layer for the GMR film. The ferromagnetic layer functions as a free layer for the TMR film.
A p-type magnetic semiconductor is used for a p-type semiconductor constituting the pn diode.
The layered element is structured to comprise a Schottky diode comprising a semiconductor and a ferromagnetic layer, a non magnetic layer, a second ferromagnetic free layer, a tunnel barrier between ferromagnetic layers, a third ferromagnetic layer which are layered in this order.
An anti-ferromagnetic layer is provided between the bit line and the third ferromagnetic layer. There is provided a tunnel barrier between diode and ferromagnetic layer between the diode and the first ferromagnetic layer.
The Schottky diode is provided with a tunnel barrier between semiconductor and ferromagnetic layer as an intermediate layer between the semiconductor ad the first ferromagnetic layer.
A layered portion of the first ferromagnetic layer, the non magnetic layer, and the second ferromagnetic layer is configured to indicate spin torque magnetization reversal. A layered portion of the second ferromagnetic layer, the tunnel barrier between ferromagnetic layers, and the third ferromagnetic layer is configured to indicate a tunnel magnetoresistance effect.
Magnetization reversal causes the second ferromagnetic layer to function as a free layer.
The first and third ferromagnetic layers are configured to provide a fixed magnetization direction. A magnetization direction of the third ferromagnetic layer is configured to be fixed by an anti-ferromagnetic layer formed opposite to a side facing the tunnel barrier between ferromagnetic layers.
The invention encompasses other embodiments of a device, an apparatus, and a method which are configured as set forth above and with other features and alternatives.